1. Field
Example embodiments of the following description relate to an image restoration method and apparatus that may reduce an external memory bandwidth during restoring of a current image.
2. Description of the Related Art
In general, when a current image is restored, motion compensation may cause a large number of requests for a memory. In particular, when a large amount of data flows between a processor and a memory, a setting latency and an access latency of a Direct Memory Access (DMA), and a data transmission time may be increased, which may result in a reduction in a performance of a system.
During restoration of a current image, an optimal mode may be determined based on a motion vector and a reference image that are associated with the current image. Additionally, a skip mode may be determined for each of the blocks that form the current image. A mode of the current image may be determined to be a skip mode, when the following requirements are satisfied.
Specifically, when 1) a motion compensation block has a size of “16×16,” 2) a previous image immediately preceding the current image is used as a reference image, 3) a motion vector in “16×16” mode is identical to a motion vector of the skip mode, 4) a number of bits of residual data is “0” or an approximate value of “0,” the current image may be determined to be in the skip mode. In the skip mode, since the number of bits of residual data is “0” or an approximate value of “0,” there may be almost no difference between the current image and a predicted image, or the current image and the predicted image may be the same.
When the current image is in the skip mode, a conventional memory system may read pixel data of a reference image from a memory, without changing the pixel data. In other words, in the skip mode, the conventional memory system may compare parameters to perform an interpolation operation on the pixel data of the reference image. Additionally, when the pixel data of the reference image remains unchanged as a result of the comparing of the parameters, the conventional memory system may store the pixel data of the reference image as a current image.
Accordingly, even when an operation of changing the pixel data of the reference image is not performed, the conventional memory system may read the reference image and compare the parameters, and accordingly a bandwidth between a processor and a memory may be wasted. The operation of changing the pixel data of the reference image may include, for example, an operation of generating a predicted image, an operation of generating a residual image, and the like. In other words, due to the interpolation operation performed during motion compensation of a current image, a memory bandwidth of a Digital Signal Processor (DSP) may be wasted even when pixel data is not substantially changed.
Thus, there is a desire for a technology that may prevent a bandwidth of the DSP from being wasted when the interpolation operation, such as an operation of changing pixel data of a reference image, is not substantially performed during motion compensation.